biographer n.

1680s, "the histories of individual lives, as a branch of literature," probably from Medieval Latin biographia, from later Greek biographia "description of life" (which was not in classical Greek, bios alone being the word there for it), from Greek bios "life" (from PIE root *gwei- "to live") + graphia "record, account" (see -graphy).

The meaning "a history of some one person's life" is from 1791. The meaning "life course of any living being" is by 1854. No one-word verb form has become common; biographise/biographize (1800), biography (1844), biograph (1849) have been tried.

English agent noun ending, corresponding to Latin -or. In native words it represents Old English -ere (Old Northumbrian also -are) "man who has to do with," from Proto-Germanic *-ari (cognates: German -er, Swedish -are, Danish -ere), from Proto-Germanic *-arjoz. Some believe this root is identical with, and perhaps a borrowing of, Latin -arius (see -ary).

Generally used with native Germanic words. In words of Latin origin, verbs derived from past participle stems of Latin ones (including most verbs in -ate) usually take the Latin ending -or, as do Latin verbs that passed through French (such as governor); but there are many exceptions (eraser, laborer, promoter, deserter; sailor, bachelor), some of which were conformed from Latin to English in late Middle English.

The use of -or and -ee in legal language (such as lessor/lessee) to distinguish actors and recipients of action has given the -or ending a tinge of professionalism, and this makes it useful in doubling words that have a professional and a non-professional sense (such as advisor/adviser, conductor/conducter, incubator/incubater, elevator/elevater).