limnology n.

word-forming element used scientifically, "of or pertaining to lakes and fresh water," from Greek limne "pool of standing water, tidal pool, marsh, lake," a word of uncertain origin; the most likely guess is that it is related to Latin limus "mud," from PIE root *(s)lei- "slime" (see slime (n.)), via the notion of "moistness, standing water" [Beekes].

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.