So I was talking to the kids today. While I use the word singulatim on occasion, I've never given it much thought. I've just used it as one at a time. Then I left it at that. After all: English has once, twice, (a dead) thrice, four times, etc. Latin has semel, bis, ter, quater, etc. So I, naturally enough, figured that there just wasn't an exact overlap. I also know about distributive numbers in Latin—a neat trick.
Anyway. We were playing with Legos and I needed to get a specific piece two at a time. So instead of asking for partes binae, I asked for them binatim.
Oh well. Live and learn?