abstainyoudaoicibaDictYouDict[abstain 词源字典]
abstain: [14] The literal meaning of this word’s ultimate source, Latin abstinēre, was ‘hold or keep away’, and hence ‘withhold’ (the root verb, tenēre, produced many other derivatives in English, such as contain, maintain, obtain, and retain, as well as tenacious, tenant, tenement, tenet, tenor, and tenure).

That is how it was used when it was first introduced into English (via Old French abstenir), and it was not until the 16th century that it began to be used more specifically for refraining from pleasurable activities, particularly the drinking of alcohol. The past participial stem of the Latin verb, abstent-, gave us abstention, while the present participial stem, abstinent-, produced abstinent and abstinence.

There is no connection, incidentally, with the semantically similar abstemious, which comes from a Latin word for alcoholic drink, tēmōtum.
[abstain etymology, abstain origin, 英语词源]
abstain (v.)youdaoicibaDictYouDict
late 14c., "to withhold oneself," from Old French abstenir (14c.), earlier astenir (13c.) "hold (oneself) back, refrain, abstain (from), practice abstinence," from Latin abstinere "withhold, keep back, keep off," from ab(s)- "from, away from" (see ab-) + tenere "to hold" (see tenet). Specifically of liquor, late 14c. Of voting, 1796. Related: Abstained; abstaining.