1. To make an entreaty; that is, to beg, beseech, implore; to beg.
2. To ask someone earnestly and fervently; to entreat (to beg someone for something, often repeatedly).
3. To utter or to address a prayer or prayers to God, a god, or another object of worship.
4. Etymology: from Latin precari which meant "to ask for, to entreat, to pray".

In Vulgar Latin, it became precare, which passed into English via Old French preier.

The noun prayer goes back ultimately to the Latin adjective precarius, "obtained by asking or praying".