Is "shot my wad" acceptable in the workplace?

So here, my friends, is my topic of discussion for today.  My boss, for whom I have a great deal of respect and have never had any reason to suspect him of being a sexist pig, has twice used the phrase "shot my wad" in conversation with me.  As in, "I don't think we can put together another grant this year.  We shot our wad on the last one".  Nice, right?  I get major props for keeping my facial features in line.  When the actual words he had said registered in my brain, the urge to allow my eyebrows to merge with my hairline was practically involuntarily.  However, I give a shit what Boss thinks of me, so I kept it together.  He probably thought I had a nervous twitch.  Out loud I managed a noncommittal, "huh, that's too bad" response while inside my brain was shouting, "Holy shit! Did he really just say what I think he just said??"

So, that was the first time Boss used this phrase. Yes, there was a second.  Once, I can pass off as an inadvertent slip.  But twice?  Now I'm curious. "Shot my wad"  from a man that I have never even heard use one of the good curse words.  Surely "fuck" comes earlier in the inappropriate work language lexicon than "shot my wad"?? 

Let's dissect the possibilities.  First, he uses the phrase so frequently that it no longer means what it actually means. I can just see this mild mannered scientist talking to a waitress, "I would go for dessert, but I shot my wad on that entree".  Or turning down a girl scout, "Sorry, no cookies for me.  I shot my wad on a boy scout and his popcorn." See how wrong this is??

Second possibility: he doesn't really know what it means.  He just thinks it is a colorful way of saying, "I am all done".  Possible, but unlikely.  He is a grown man with an advanced degree.  More to the point, he has a teenage son.

Last possibility. Boss just doesn't see anything wrong with using that phrase in conversation with a female colleague....

Ding ding ding.  I think we have a winner.