c. 1300, preiere, "earnest request, entreaty, petition," also "the practice of praying or of communing with God," from Old French prier "prayer, petition, request" (12c., Modern French prière), from Medieval Latin precaria "petition, prayer," noun use of Latin adjective precaria, fem. of precarius "obtained by prayer, given as a favor," from precari "to ask, beg, pray" (from PIE root *prek- "to ask, entreat").
From mid-14c. as "devout petition to God or a god or other object of worship;" also "the Lord's Prayer;" also "action or practice of praying." Related: Prayers. Prayer-book "book of forms for public or private devotions" is attested from 1590s; prayer-meeting "service devoted to prayer, sacred song, and other religious exercises" is from 1780. Prayer-rug "small carpet spread and used by a Muslim when engaged in devotions" is by 1898 (prayer-carpet is by 1861). To not have a prayer "have no chance" is from 1941.
Proto-Indo-European root meaning "to ask, entreat."
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.
c. 1200, "solemn prayer of supplication," from Old French letanie (13c., Modern French litanie) and directly from Medieval Latin letania, Late Latin litania (source also of Spanish letania, Italian litania), from Greek litaneia "prayer, an entreating," from lite "prayer, supplication, entreaty," a word of unknown origin. From the notion of monotonous enumeration of petitions in Christian prayer services came the generalized sense of "repeated series" (early 19c.), which originated in French.
For those who know the Greek words, a litany is a series of prayers, a liturgy is a canon of public service; the latter in practice includes prayer, but does not say so. [Fowler]
c. 1200, orisoun, "a prayer," especially "a set prayer that forms part of a religious service," from Anglo-French oreison, Old French oreisun (12c., Modern French oraison) "oration," from Latin orationem (nominative oratio) "speech, oration," in Church Latin "prayer, appeal to God," noun of action from past-participle stem of ōrare "to speak, pray, plead" (see orator). Etymologically, a doublet of oration.
"supplication, prayer," c. 1300, verbal noun from beseech. As a present-participle adjective from 1704. Related: Beseechingly; beseechingness.