Prithee is an archaic English interjection formed from a corruption of the phrase pray thee ([I] ask you [to]), which was initially an exclamation of contempt used to indicate a subject's triviality.
[1] The earliest recorded appearance of the word prithee listed in the Oxford English Dictionary is from 1577, while it is most commonly found in works from the seventeenth century.
[5] There has been extensive scholarship investigating the difference in usage of prithee as opposed to pray you, both in terms of politeness and grammaticalisation.
Prithee and pray you often coincide in Early Modern English texts, and the difference between the two terms has been debated by scholars.
Wider repercussions are observable in the replacement of such phrases as "excuse me" and "pardon me," which request understanding or forgiveness, with "I am sorry," which instead acknowledges the speaker's remorse.