Easiest and least confusing way to do it is to ask Siri for your name pre-expletive change and then tap the white address card. Fill in your bad words in the first name field and listen to her spew curse words.
Words that can trigger your Amazon Echo ($60 at Amazon) when you have "Alexa" set as the wake word include Lexus, Alexis, Elixir and Lexa.
