Expanding to the peripheries: A corpus-based study of the development of the Japanese discourse marker toiuka

- Toiuka originally expressed the speaker's difficulty in lexical choice.
- Subsequently, it shifted its position and gained new uses.
- In the left periphery, it serves the purposes of repair, upgrade, and disagreement.
- In the right periphery, it adds elaboration or weakens assertiveness.
- The left periphery shows more vigorous change.

Many languages have common or stock phrases that are used when the speaker is unsure about how to say a certain thing, as with such English expressions as how should I put it? and something like X. In conversation, one strategy to avoid turning into a silence is to give a tentative choice with the hope that the addressee will understand the speaker's meaning. The Japanese discourse marker toiuka started as such a parenthetical expression that appears in mid-sentence and indicates the speaker's difficulty in lexical choice. It subsequently shifted to the utterance-initial and -final positions and gained new uses. The present article examines the diachronic development of this expression, using data from the National Diet Minutes Corpus [1], the Ninjobon 'Love Story Books' Corpus [2], and the Taiyo 'Sun Magazine' Corpus [3]. We keep track of the pragmatic-semantic and syntactic patterns over time quantitatively and show from a usage-based approach how this gradual process occurred.