Don't worry. The interesting part isn't as geeqy as it may look from here.
is the abbreviation for
--pronounced bilshon am zar--which means "in the language of a foreign people." It's used by Hebrew writers on religious matters when they're forced to use a non-Hebrew word (written in Hebrew letters) to make themselves clear. Rashi, for example, would write בלע״ז when using a then-modern French word. I translate בלע״ז as "in Gentilic jargon."
This is all by way of introduction to something interesting (to me). In Sefer diqduq l'Ramhal (The grammar book of Rabbi Moshe Hayyim Luzzatto), edited and annotated by Eluzer Brieger of Brooklyn (Bnei Brak: Mishor, ), page 25, note 2, we find this:
Or, in English, "...פְּעוּלָה is what we call aktiv in Gentilic jargon, while הִפָּעֵל is what we call pessiv."
So why not either both aktiv and passiv, or both ektiv and pessiv? We can sort of guess why each was chosen (and we shouldn't forget that these are guesses). Aktiv seems more scholarly and Continental, and is in fact consistent with the spelling in English; pessiv seems to reflect what I assume to be Reb Eluzer's pronunciation of English. Each makes sense on its own terms, but the combination is interesting. I'm not going to try to get any big meanings out of it.
For the record, although this shouldn't be necessary, I'm not making fun of anything--neither Reb Eluzer's presumed accent nor the apparent inconsistency.
I spent the night regretting that I didn't include this.
In the comments on pessiv there was an unstated but blatant circularity. Why did Reb Eluzer write pessiv? Because he speaks English with a Yiddish accent. And how do I know he has a Yiddish accent? Because he wrote pessiv. This is such a nice circle that you can use it for your geometry homework.
And how do I even know pessiv reflects a Yiddish accent? Well, I don't actually know that it does. Maybe it reflects a plain ordinary U.S.A. accent. Consider the words "active" and "passive." We don't pronounce the noun in the first syllable like an "ah." We pronounce it æ. It's the sound that we use in "æccent," "æt," and "ænd"; it's the sound BBC news readers use in "Nicarægua" and "Jæck Cheeræck." Yiddish doesn't have (or hæve) the æ sound. Pessiv is as reasonable an approximation of "pæssive" as passiv would be.
And it's still interesting that two different vowels were used in the Gentilic jargon for "active" and "passive."