Uhm. Well my daddy is a bit of a gym rat so... The first time I gave him a blow job (also happened to be my first ever blow job, yikes) and I, of course, swallowed (being the good girl that I am), I referred to it as a 'protein shake' jokingly. So now whenever he wants a blow job he'll usually ask me 'do you want daddy's protein shake now?' and... well it's kinda hot, kinda funny.
I find the term 'daddy's cock' so, so, so hot. But, again I can understand how some people wouldn't be into it. So I suppose it depends on if you want to be vague so things like;
So on and so forth.
Or if you want to be more direct;
So on and so forth. Wording isn't necessarily important to me though, as long as you don't say 'dick' (hate that word in a sexual context, it's my #1 turn off, idk why) I'm good. It varies from person to person and couple to couple though; it's better to ask your partner directly or just figure out what you like best.