mid-14c., restreinen, "to stop, prevent, curb" (a vice, purpose, appetite, desire), from stem of Old French restraindre, restreindre "to press, push together; curb, bridle; bandage" (12c.), from Latin restringere "draw back tightly, tie back; confine, check" (see restriction).

From late 14c. as "keep (someone or something) from a course of action," hence "keep in check or under control, deprive (someone) of liberty by restraint" (1520s). Related: Restrained; restraining; restrainer; restrainable.

That which we restrain we keep within limits; that which we restrict we keep within certain definite limits; that which we repress we try to put out of existence. [Century Dictionary, 1902]

1520s, "a holding off, refusal to do something," from French abstention (Old French astencion), from Late Latin abstentionem (nominative abstentio) "the act of retaining," noun of action from past-participle stem of Latin abstinere/abstenere "withhold, keep back, keep off," from assimilated form of ab "off, away from" (see ab-) + tenere "to hold" (from PIE root *ten- "to stretch"). As "a refraining from voting" by 1859.

late 14c., "avoid (something); refrain (oneself) from; keep free from sin or vice; live austerely, practice abstinence or asceticism; be sexually continent," from Old French abstiner, abstenir (14c.), earlier astenir (13c.) "hold (oneself) back, refrain voluntarily, abstain (from what satisfies the passions), practice abstinence," from Latin abstinere "withhold, keep back, keep off," from assimilated form of ab "off, away from" (see ab-) + tenere "to hold," from PIE root *ten- "to stretch." Specifically of liquor from late 14c. Meaning "refrain from voting" is from 1796. Related: Abstained; abstaining.

c. 1400, "an official entrusted with the power and the duty to protect the interests or rights of someone else or some thing," from Anglo-French conservatour, from Latin conservator "keeper, preserver, defender," agent noun of conservare "to keep, preserve, keep intact, guard," from assimilated form of com-, here perhaps an intensive prefix (see com-), + servare "keep watch, maintain" (from PIE root *ser- (1) "to protect").

General sense of "a preserver" (from injury, violation, etc.) is from mid-15c. Fem. form conservatrice was used mid-15c. in reference to the Virgin.

1755, "commission with jurisdiction over a port or river," from -cy + Latin conservant-, present-participle stem of conservare "to keep, preserve, keep intact, guard," from assimilated form of com-, here perhaps an intensive prefix (see com-), + servare "keep watch, maintain" (from PIE root *ser- (1) "to protect").

Earlier was conservacy "preservation under law, protection" (mid-15c., Anglo-French conservacie). The meaning "official preservation of undeveloped land" dates from 1859 (first reference is to the protection of bo trees in Ceylon). General sense of "act of preserving" is by 1832. Meaning "institution concerned with the preservation of nature, undeveloped land, etc." is by 1949.

transitive, "to keep secret, conceal, hide" (marked in OED as "obsolete"), 1590s, from secret (n.). Related: Secreted; secreting.