tide

O.E. tid “point or portion of time, due time,” from P.Gmc. *tidiz “division of time” (cf. O.S. tid, Du. tijd, O.H.G. zit, Ger. Zeit “time”), from PIE *di-ti- “division, division of time,” suffixed form of base *da- “to divide, cut up” (cf. Skt. dati “cuts, divides;” Gk. demos “people, land,” perhaps lit. “division of society;” daiesthai “to divide;” O.Ir. dam “troop, company”). Meaning “rise and fall of the sea” (1340) is probably via notion of “fixed time,” specifically “time of high water;” either a native evolution or from M.L.G. getide (cf. also Du. tij, Ger. Gezeiten “flood tide”). O.E. had no specific word for this, using flod and ebba to refer to the rise and fall. The verb meaning “to carry (as the tide does)” is recorded from 1626, usually with over.

To enable you to overcome or endure a difficulty.

When something is “tiding you over” you are, in a sense, being temporarily lifted or enabled to float over the emergency.