弖爾乎波) - written as
てにをは - is a term used to refer to the Japanese particles (
助詞) or sometimes Japanese grammar as a whole (
文法). So how to do pronounce the
は at the end? Is it
ハ? Presumably it's the former since it's describing particles, but I've never seen it definitively explained anywhere.
According to the entry about は in デジタル大辞泉:
Which is probably the source of confusion. If one thinks of it as a "word" then they might be inclined to read it as
However, according to the entry about てにをは in デジタル大辞泉:
So, as you can see, it's more like an acronym of sorts than it is an actual "word" (as in it identifies the markup actually used in
漢文). Therefore, it is read as
伊呂波短歌) is read as
i-ro-ha and not
i-ro-wa (I have no sources to back up this claim, though, other than my own experience).
The は is being used as the pronunciation of 波, and not as a particle. Thus it is pronounced like a ハ. The particle は is always in the hiragana form, so as it is a kanji it must be pronounced ハ.
Just because it is describing particles does not mean it is a particle.
Remember, if は is the pronunciation of a kanji, it is always pronounced ハ. Only when it is a particle (when it must be in hiragana form) can it pronounced ワ.