initial (adj.) Look up initial at Dictionary.com
1520s, "of or pertaining to a beginning," from Middle French initial or directly from Latin initialis "initial, incipient," from initium "a beginning, an entrance," from past participle stem of inire "to go into, enter upon, begin," from in- "into, in" (see in- (2)) + ire "to go" (see ion).
initial (n.) Look up initial at Dictionary.com
"initial letter of a name or surname," 1620s, from initial (adj.) in a specialized sense "standing at the beginning of a word, sentence, etc."
initial (v.) Look up initial at Dictionary.com
"to mark or sign with initials," 1864, American English, from initial (n.). Related: Initialed; initialing.