Great question! Being a person sometimes intensely aroused by a single word or single mental image, I appreciate this question.
For me, the trigger words vary over time. There was a period of several years, when the word “enema,” in any circumstance, would start the juices flowing involuntarily. If I just encountered the word, I was going to be aroused until I could have a release by masturbation or intercourse. Masturbation was better really, because I could focus on the naughty word and the images it triggered.
Most recently, I came to be sensitized to the word “ejaculation.” I cannot explain this exactly, but my wife very unexpectedly used this word in the context, “you just need to have a good ejaculation.” It was a word that I would not have expected her to say, and the exact description of precisely what I needed. I just needed to deeply and fully ejaculate my pent up load. For some unexplained psychological reason that so sensitized me to the word “ejaculate,” the thought of it or the use of it, especially by my wife, arouses me and moves me towards climax.
Over the years, other words have come and gone. For quite a while the word “suppository” would trigger me. “Vulva” did briefly. More often, it was expressions. The term to “take down panties” has been good for seemingly ever. “Honey, Mommy is going to have to give you an enema” has come and gone several times. A list of such provocative terms could go on and on.