The Collaborative International Dictionary of English v.0.48:
Swearer \Swear"er\, n. 1. One who swears; one who calls God to witness for the truth of his declaration. [1913 Webster] 2. A profane person; one who uses profane language. [1913 Webster] Then the liars and swearers are fools. --Shak. [1913 Webster]WordNet (r) 3.0 (2006):
swearer n 1: someone who uses profanity 2: someone who takes a solemn oath