Spay? Spade? What The Heck?

I sometimes get random, strange thoughts, and today one occurred to me. I have been in veterinary medicine for about 25 years, and have always know that a spay is when you remove the reproductive organs from a female. I've always accepted that and never really thought about it. But today for some reason it suddenly dawned on me that the word didn't make sense.

The proper term for the surgery is ovariohysterectomy. Where do you get "spay" out of that word? A castration is called a neuter, and is used only for males. I can understand neuter, as you're kind of changing a male into a neutral. But what about the word spay? Word origins often interest me, so I tried looking it up. The problem is that it still doesn't make sense!

Here's what an online etymology dictionary has for "spay":
c.1410, "stab with a sword, kill," also "remove the ovaries of," from Anglo-Fr. espeier "cut with a sword," from M.Fr. espeer, from O.Fr. espee "sword" (Fr. épée), from L. spatha "broad, flat weapon or tool," from Gk. spathe "broad blade" (see spade (1)).

So basically the word "spay" refers to cutting someone. How this ended up being specific to removing a female animal's reproductive tract, I still don't know. And if anyone else knows, I'd love to hear from you!

Believe it or not, strange and random thoughts like this are not uncommon for me!