Proto-Indo-European root meaning "to be strong."
It forms all or part of: ambivalence; Arnold; avail; bivalent; convalesce; countervail; Donald; equivalent; evaluation; Gerald; Harold; invalid (adj.1) "not strong, infirm;" invalid (adj.2) "of no legal force;" Isold; multivalent; polyvalent; prevalent; prevail; Reynold; Ronald; valediction; valence; Valerie; valetudinarian; valiance; valiant; valid; valor; value; Vladimir; Walter; wield.
It is the hypothetical source of/evidence for its existence is provided by: Latin valere "be strong, be well, be worth;" Old Church Slavonic vlasti "to rule over;" Lithuanian valdyti "to have power;" Celtic *walos- "ruler," Old Irish flaith "dominion," Welsh gallu "to be able;" Old English wealdan "to rule," Old High German -walt, -wald "power" (in personal names), Old Norse valdr "ruler."
1580s, "to estimate the value of; value highly," spelling alteration of Middle English prisen "to reckon the worth of, value, esteem, praise" (late 14c.), from stem of Old French preisier "to praise" (see praise (v.)). Related: Prized; prizing.
1767, "a lowering of value" (originally of currency), noun of action from depreciate. Sense of "a belittling, deliberate underestimation of the merits of a person, action, or thing" is from 1790. Meaning "loss of value of a durable good by age or wear" is from 1900.
1650s, "to esteem or value highly," from Late Latin appretiatus, past participle of appretiare "to set a price to," from ad "to" (see ad-) + pretium "price" (see price (n.)). Meaning "to rise in value" (intransitive) is by 1787; sense of "be fully conscious of" is by 1833. "Appreciate is to set a just value on; it implies the use of wise judgment or delicate perception" [Century Dictionary]. Related: Appreciated; appreciating.