The first topic promised in the overview article is the sound of the ha-row. Say these words aloud.

Not “-hoi” or “-boi,” but “-poi.” Is this ending originally “hoi”? In “P-on-kō” in Kokugo no tame, Part 2 (1903), Ueda Kazutoshi places these very examples at the center of his argument.

Alone it’s “ha,” in a compound it’s “pa”

Ueda observes: something pronounced in the ha-row (h) when alone always becomes the pa-row (P) once it enters a compound. Okorippoi, shimeppoi, and Satsumappō are the examples.

Ueda reasons out why: that they become pa-row only in compounds suggests that the pronunciation habits of high antiquity remain, as a trace, inside compounds. We follow that old habit without realizing it.

"Ha" alone, "pa" in a compound okori + ppoi shime + ppoi Satsuma + ppō Ueda's inference: an old P sound survives inside compounds P → ph/f → H (the course of the ha-row sound) Examples are Ueda's own. Diagram: ToL
P surviving inside compounds. Diagram: ToL

Two possibilities Ueda distinguished

Ueda, however, carefully separates two possibilities.

That is, he doesn’t claim that examples like okorippoi are all direct survivals of the old P. He says there may also be cases where a word with H turns into P, pulled by an old habit.

The sounds of “pachi-pachi” and “pin-pin”

Ueda points to another familiar fact. P sounds, he says, are easy to pronounce — even an infant under a year old can make them. In Japanese, sound-symbolic words (onomatopoeia) such as pachi-pachi, bara-bara, pishi-pishi, pin-pin, potsu-potsu, and pon-pon use P and B sounds quite ordinarily. And we pronounce and understand them without effort.

So Ueda says: it is rather strange to claim that the ancient Japanese struggled with the pa-row sounds when practicing foreign sounds. Such sounds, he suggests, must have been in Japanese from the start.

The path to the modern ha-row

So how did the ha-row sound change? Ueda reasons that, just as today’s ha hi fu he ho are pronounced moving toward wa ki u e o, the old pa pi pu pe po existed before the Nara period and gradually moved to ha hi fu he ho. Between them he posits a sound like ph, or f.

What this article introduces is Ueda’s inference. How it is assessed in present-day research, we sort out in the verdict article. What evidence Ueda piled up for the conclusion, we read in the close-reading article.

Summary

PointDetail
ObservationWords in the ha-row alone become pa-row in compounds (okorippoi, shimeppoi, Satsumappō)
Ueda’s inferenceThe ha-row was once P, and that habit leaves traces in compounds
Two possibilitiesA direct survival of old P, or an H word turned P by the old habit
Path of changeP → ph/f → H

In a nutshell — Ueda Kazutoshi thought the “po” of okorippoi was a clue that the ha-row of Japanese was originally a P sound. Its trace remains inside compounds even now.