Unexpected singular and plural

These are in a letter about the death of a girl.

Ut illa patris cervicibus inhaerebat. Oh how she used to cling to her father’s neck. But why is cervix plural?

And later, when her father is listing what he was going to buy for her upcoming wedding:
quod in vestis, margarita, gemmas fuerat erogaturus. Why is margarita singular here? Were pearls so very expensive?

Phil

Cervix is actually found more commonly in the plural than the singular, even when referring to just one neck. There’s no real logic to this, it’s just another plurale tantum word, similar to fauces “the throat”.

I’m not sure why margarita is singular. I guess there was only one.

A rare variant (according to L&S and OLD) is margaritum.
margarita (feminini generis) seu margaritum (verbum neutrius generis et perrarum, secundum A&S et OLD)

Exactly hat Adrianus said and cited…

When you look at the bones and components of the neck, there are lots of them, which might have something to do with it.
Numerosae sunt partes et ossa (vertebrae C1-7) cervicium seu faucium, quod forsit ad rem pertineat.