When did 'post' become a popular replacement of the word 'after'

Solution 1:

post-, a prefix OED

Formations with second elements not of Latin or Greek origin are first found in the 17th or 18th centuries (e.g. in the 17th cent. perhaps post-talmudical adj. at sense 2a(b)(iv)(1) and post-law n. at sense 1a(b)(ii)(2), in the 18th cent. post-breakfast adj. at sense 2a(a)(i), post-Kantian n. and adj. at sense 2a(b)(i)); such formations become particularly common in the 20th cent.

It appears using the post- prefix with the following noun being English appeared in the 14th century and became most common in the 1900+ period. I even see a listing for post 16, ie after the age of 16 years old.

Formations after Latin models first appear in English in the late 14th cent. (in an apparently isolated attestation: post-common n.) and then again from the 16th cent. (e.g. post-dissension n., postbrachial adj. at sense 2b); the first direct borrowing from Latin is apparently postpone v. in the late 15th cent.; there are also some borrowings from Middle French before the end of the 16th cent. (e.g. post-communion n., postpose v.). From the end of the 16th cent., most formations are within English, although there are still a number of borrowings directly from Latin (e.g. postpredicament n., postscribe v.) and formations after Latin models.