The first word promised in the overview article is itoshi. It is the old word behind today’s itoshii, but in his 1937 lecture “Kokugo to minzokugaku,” Orikuchi Shinobu explains that this word seems originally to have had the opposite meaning.

Today’s itoshii

Modern itoshii is used like this.

Lovable, precious, hard to part from — a word of affection. But according to Orikuchi, the itoshi it came from had shifted greatly in meaning around the Heian period.

Originally, “unpleasant”

Orikuchi explains: itoshi took the word itou (“to shun”) as its root and made it into an adjective. And its central meaning, he says, seems to have been a feeling of “unpleasant.”

Itou is a verb still used today, as in rō o itowanai (“not shrink from the labor”), meaning to dislike, to avoid. Its adjective form would naturally mean “unpleasant” or “off-putting.”

“Pulled along” by another word

So why did it come to mean something near “dear”? Orikuchi’s explanation is this.

In the Heian period there was another word, itawashi. Rooted in itamu (“to ache”), it carried senses like “painful to see” or “pitiable.” Itawashi and itoshi were very close in form. So, he says, itoshi was pulled along by itawashi toward its meaning.

As a result, Heian tales and diaries show these uses mixed together:

Orikuchi points out that there are many such “in-between” examples in tales and diaries. Reading them today, we can translate them as either “dear” or “unpleasant.” But people of the time the word was in use had a clear sense of that in-between — so once that era passes and the word is forgotten, that subtle feeling can no longer even be imagined.

itoshi (old sense) root itou = unpleasant In between (Heian tales) "unpleasant" or "pitiable" itoshii (later sense) dear, precious itawashi ache, pitiable pulls A similar-looking word pulls the meaning along
The change in itoshi (as Orikuchi Shinobu explains it). Diagram: ToL

Meaning is something that moves

The idea that “meaning moves when pulled by a similar-looking word” is an easy-to-follow picture for thinking about changes in word meaning. But what this article introduces is Orikuchi’s explanation in a lecture. That the etymology is rooted in itou is an idea ordinarily given in classical-Japanese dictionaries too. The part about “being pulled by itawashi” is Orikuchi’s interpretation, and is best read as one plausible way of explaining the shift in meaning.

Summary

PointDetail
Today’s meaningItoshii = lovable, held dear
Original meaningItoshi took itou as its root, and seems to have centered on “unpleasant”
Why it changed (Orikuchi’s explanation)Pulled toward the similar-looking itawashi (ache, pitiable)
In Heian usageMany in-between uses, between “unpleasant” and “pitiable,” in tales and diaries

In a nutshellitoshi was originally a word meaning “unpleasant.” Pulled by the similar-looking itawashi, it gradually shifted toward “pitiable” and “dear,” Orikuchi Shinobu explained.