草そう々そう不ふ一いつ

Meanings

Sincerely yours; with apologies for brevity

Formal letter closing phrase used when the writer apologizes for the letter's brevity or informal style. Implies the letter was written hastily or without full formality.

手て紙がみの最さい後ごに「草そう々そう不ふ一いつ」と書かいて結むすんだ。
I closed the letter with 'Sincerely yours (with apologies for the brevity).'

Kanji

草grass, weeds, herbs
不negative, non-, bad
一one, one radical (no.1)

Related words

草そう々そう
草々 is a simpler closing meaning 'Sincerely yours' without the explicit apology for brevity. 草々不一 adds the nuance of 'please excuse the rough/informal writing'.
不ふ一いつ
不一 alone means 'not one' or 'incomplete', and in letter closings it implies the letter does not fully express the writer's thoughts. Combined with 草々, it strengthens the apology for brevity.

Written forms

草そう々そう不ふ一いつ
Standard kanji form used in letter closings.
草そう草そう不ふ一いつ
Variant kanji form; 草草 is an alternative repetition of 草.

Etymology

Composed of 草々 (sōsō, 'sincerely yours' or 'roughly written') and 不一 (fuitsu, 'not one' or 'incomplete'). The phrase literally suggests the letter is hastily written and does not fully convey the writer's feelings.