Words in Pali have several meanings (sometimes subtly related) .
We have seen that anicca means "impermanent"; or else it means "not one's own".
We have seen that sati means "mindfulness" (as keeping unwanted phenomena outside the internal); or else that it means "obtention".

Does sampajāna always mean "clearly comprehending" (transl. Bodhi), ["situational awareness" (transl. Sujato) | "alert" (transl. Thanissaro)], OR does it also mean: "produced/sprung by/from the nose/breath".
In these two cases however, the roots are utterly different, and so are the meanings.

Sampajāna (sam-prajā-āna) is not to be confounded with sampajāna (sampajañña [saṃ-pa-jña]).


Sampajāna(adj.)[saṁ+pajāna = saṁ+paja-ana ]

prajā + āna

प्रजा prajā (प्रज pra-ja - [ pra-√ jan]).
- propagation , birth RV. AV.

प्रजन् prajan [ pra-√ jan ]
- to be born or produced , spring up from, be begotten by-from-or with, arise from. RV.
- to bring forth , generate MBh.
- to wish to cause to be conceived or born ŚBr.

आन āna (fr. √ an)
- nose RV.
- breathing

√ अन् an
- to breathe , respire ; to live.


Then the following extract would translate as follow:

Etha tumhe, āvuso, kāye kāyānupassino viharatha ātāpino* sampajānā** ekodibhūtā*** vippasannacittā**** samāhitā**** ekaggacittā, kāyassa yathābhūtaṃ ñāṇāya;
vedanāsu vedanānupassino viharatha... etc.
Come, friends, fetch distinctively the noticeable body (viz. breath) from the bodies, ardent*, arising from the nose**, "that has become transcended to one***", with a citta that has clear and serene distinction into phenomena****, with serenity of the "establishment" (samādhi) [of citta]****, with oneness of citta; in order to know the body as it has come to be. Dwell contemplating feelings in feelings … etc.
SN 47.4

* ātāpino = ardent
In Sanskrit, तापिन् tāpin [agt. तप् √ tap] means heating up >> ā+tāpin = towards heating up.
The "ardent" breathing above (towards heating up,) remains a mild तपस् tapas, however.

** as developped above.

*** (Eka) + udi (transcend - escape) उदि udi [ ud-√ i].
Ekodibhūtā = that has become transcended to one.
Here, "one" does not imply "joined into a single"; but "having the character of a pristine unit".
When it comes to breath, it means a breath as a whole, without anything else involved.
When it comes to citta, it means a citta that is not polluted by the influence of mano. A native, pristine unmingled citta.

"One" means original; namely, not by way of something added. 


**** Note that the concept of "sama­tha­-vi­passa­na", as being developped in different order (e.g. samatha first, or vipassana first, or both together, appears only in AN 4.170, a sutta that does not have a parallel for that particular concern). Even in MN 151, (the only other occurence of "sama­tha­vi­passa­na"), there is no parallel.
We might conclude in a progression:
vippasanna >> samāhitā.
Which would go pretty well with:

"But if, by such self-examination, he knows: ‘I gain the higher discernment of the serene distinction into phenomena but not internal serenity of citta, he should base himself on the higher discernment of the serene distinction into phenomena, and make an effort to gain internal (serenity of) establishment citta. Then, some time later, he gains both the higher discernment of the serene distinction into phenomena and internal serenity of the establishment of citta.
Sace pana, bhikkhave, bhikkhu paccavekkhamāno evaṃ jānāti: ‘lābhīmhi adhipaññādhammavipassanāya, na lābhī ajjhattaṃ cetosamathassā’ti, tena, bhikkhave, bhikkhunā adhipaññādhammavipassanāya patiṭṭhāya ajjhattaṃ cetosamathe yogo karaṇīyo. So aparena samayena lābhī ceva hoti adhipaññādhammavipassanāya lābhī ca ajjhattaṃ cetosamathassa.
AN 10.54 (perfectly paralleled in MA 109).
See here

Another extract gives the following:

Bhikkhus, to whatever extent I wish, with the fading away as well of rapture, dwelling as seeing it with my citta (upekkhako*), having obtained (it/the breath**) and springing from the nose (sampajāno), I experience happiness with the body (breath); I enter and dwell in the third jhāna...
Ahaṃ, bhikkhave, yāvadeva ākaṅkhāmi pītiyā ca virāgā upekkhako ca viharāmi sato ca sampajāno sukhañca kāyena paṭisaṃvedemi, yaṃ taṃ ariyā tatiyaṃ jhānaṃ upasampajja viharāmi....
SN 16.9

upekka (upa + īkṣ)
उपेक्ष् upekṣ [ upa-√ īkṣ ] )
- to look at or on - ŚBr. & MBh.
√ ईक्ष् īkṣ
- gaze at; to watch over AV. AitBr. ŚBr.
- to see in one’s mind (citta) ŚBr. ChUp. MBh.

** Note that Anapanasati does not mean mindfulness of breathing, but "obtention" (sati) of the breath (that is to say, an accurate knowledge of it (paṭisaṃvedī [Sk. पततससववद pratisaṃvid]).


On the other end, a good example of sampajāna as saṃ-pa-jña (clearly comprehending), is found in:


But, Bhante, there are clansmen who have gone forth from the household life into homelessness out of faith, who are not crafty, hypocritical, deceptive, restless, puffed up, vain, talkative, and rambling in their talk; who keep guard over the doors of the senses; who are moderate in eating, intent on wakefulness, intent upon the ascetic life, keenly respectful of the training; who are not luxurious and lax; who discard backsliding and take the lead in solitude; who are energetic, resolute, mindful, clearly comprehending, concentrated, with one-pointed minds, wise, intelligent. When I speak to them in such a way, they respectfully accept what I say.”
Ye pana te, bhante, kulaputtā saddhā agārasmā anagāriyaṃ pabbajitā asaṭhā amāyāvino aketabino anuddhatā anunnaḷā acapalā amukharā avikiṇṇavācā indriyesu guttadvārā bhojane mattaññuno jāgariyaṃ anuyuttā sāmaññe apekkhavanto sikkhāya tibbagāravā na bāhulikā na sāthalikā okkamane nikkhittadhurā paviveke pubbaṅgamā āraddhavīriyā pahitattā upaṭṭhitassatino sampajānā samāhitā ekaggacittā paññavanto aneḷamūgā, te mayā evaṃ vuccamānā padakkhiṇaṃ gaṇhantī”ti.
AN 5.167


In full awareness he speaks falsehood (lit. being acquainted with lie), for his own ends, or for another’s ends, or for some trifling worldly end.
Iti attahetu vā parahetu vā āmisakiñcikkhahetu vā sampajānamusā bhāsitā hoti.
MN 41


Bhikkhus, (1) one speaking rightly would say of Nanda that he is a clansman, (2) that he is strong, (3) that he is graceful, and (4) that he is strongly prone to lust. How else could Nanda lead the complete and pure spiritual life unless (5) he guarded the doors of the sense faculties, (6) observed moderation in eating, (7) was intent on wakefulness, and (8) possessed mindfulness and clear comprehension?
Kulaputto’ti, bhikkhave, nandaṃ sammā vadamāno vadeyya. ‘Balavā’ti, bhikkhave, nandaṃ sammā vadamāno vadeyya. ‘Pāsādiko’ti, bhikkhave, nandaṃ sammā vadamāno vadeyya. ‘Tibbarāgo’ti, bhikkhave, nandaṃ sammā vadamāno vadeyya. Kimaññatra, bhikkhave, nando indriyesu guttadvāro, bhojane mattaññū, jāgariyaṃ anuyutto, satisampajaññena samannāgato, yehi nando sakkoti paripuṇṇaṃ parisuddhaṃ brahmacariyaṃ carituṃ.
AN 8.9

This latter meaning applies for instance to the following suttas with parallels:
SN 36.7 (正智 correct cognition)
SN 47.2
SN 47.10
[The three above suttas might be a bit confusing, because they adress both contexts - Is it that one should be aware of one's breath in any event like walking, eating, drinking, etc.? ].