I was a bit confused, too, but I looked up the wiktionary for this term, and got this:
Noun. ulterior motive (plural ulterior motives) An alternative or extrinsic reason for doing something, especially when concealed or when differing from the stated or apparent reason.
My two main fetishes are 1) girls in medically necessary protective masks, and 2) girls in footed pajamas. The origins of both of these fetishes couldn't be more straightforward in my eyes.
Masks are my medfet, and I got into seeing female patients in masks through my interest in medical documentaries, which in turn was born by my own inpatient experiences, of which I have many.
Footed pajamas are more on the ABDL spectrum, I think, and that can be traced to a singular instance where I was at my babysiter's house one night. She called for both of her daughters to get into their pajamas. When they came out, the older one was dressed in a footed onesie (or what we called "blanket sleeper" back then). One piece, pink, with feet, vinyl soles, and vinyl toecaps.
Nothing ulterior about any of this, I don't think, though I will confess that certain masks look like gags somewhat. When I aw my friend in her half mask cartridge respirator at a dance one time before her lung transplant, it definitely looked like a gag, and that by wearing her mask, she was being forced to be silent. I knew better, of course, but it did have that kind of look to it.