prithee

early 13c., preien, "ask earnestly, beg (someone)," also (c. 1300) in a religious sense, "pray to a god or saint," from Old French preier "to pray" (c. 900, Modern French prier), from Vulgar Latin *precare (also source of Italian pregare), from Latin precari "ask earnestly, beg, entreat," from *prex (plural preces, genitive precis) "prayer, request, entreaty," from PIE root *prek- "to ask, request, entreat."

From early 14c. as "to invite." The deferential parenthetical expression I pray you, "please, if you will," attested from late 14c. (from c. 1300 as I pray thee), was contracted to pray in 16c. Related: Prayed; praying.

Praying mantis attested from 1809 (praying locust is from 1752; praying insect by 1816; see mantis). The Gardener's Monthly of July 1861 lists other names for it as camel cricket, soothsayer, and rear horse.

Proto-Indo-European root meaning "to ask, entreat." 

It forms all or part of: deprecate; deprecation; expostulate; imprecate; imprecation; postulate; pray; prayer; precarious; precatory; prithee.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit prasna-, Avestan frashna- "question;" Sanskrit prcchati, Avestan peresaiti "interrogates;" Latin precari "ask earnestly, beg, entreat;" Old Church Slavonic prositi, Lithuanian prašyti "to ask, beg;" Old High German frahen, German fragen, Old English fricgan "to ask" a question.