Japanese snowbell; Styrax japonica
A deciduous tree native to Japan, known for its white bell-shaped flowers in late spring. The name エゴノキ comes from the saponin-containing fruit that was used as a soap substitute (egosaponin).
When I planted a Japanese snowbell in the garden, it bloomed with many white flowers in spring.
The fruit of the Japanese snowbell contains saponin and was used as a soap substitute in the past.
Kanji form is rare and mainly found in older or specialized botanical texts.
From えごい, a regional form related to えぐい “acrid; harsh-tasting,” referring to the unpleasant taste of the fruit, and 木 “tree.”