Center versus periphery

In general, the theory states that new words, often synonyms, are created in influential areas and cultural centers.

Over time, these words gradually move outward to less culturally influential areas in a ripple pattern.

One phenomenon the theory attempts to explain, for example, is the Japanese word for snail, particularly prior to the Meiji period.

In Kyoto, the capital of Japan around the time of the Edo period, there were as many as four different words for snail: dedemushi (ででむし), maimai (まいまい), katatsumuri (かたつむり), and tsuburi (つぶり).

Coincidentally, often the same single word existed in both places (in this case tsuburi (つぶり)), despite the great distance between the regions.