word-forming element meaning "a speaking, discourse, treatise, doctrine, theory, science," from Greek -logia (often via French -logie or Medieval Latin -logia), from -log-, combining form of legein "to speak, tell;" thus, "the character or deportment of one who speaks or treats of (a certain subject);" from PIE root *leg- (1) "to collect, gather," with derivatives meaning "to speak (to 'pick out words')." Often via Medieval Latin -logia, French -logie. In philology "love of learning; love of words or discourse," apology, doxology, analogy, trilogy, etc., Greek logos "word, speech, statement, discourse" is directly concerned.
word-forming element meaning "one who is immersed in or driven by," mostly from French-derived words, ultimately from Greek -logos, -logon (see -logy). Now mostly superseded by -loger, -logist except in ideologue and a few others. As a combining element meaning "kind of discourse," it is from French -logue, from Greek -logos.