长久
chángjiǔ · HSK 6
long
⏳ 长 (long) + 久 (a long time) = lasting a long time
长 means long in length or duration; 久 specifically means a long period of time. Stacking the two synonyms intensifies the meaning into permanent or enduring. Common in 长久之计 (a long-term plan).
长 — pictograph of long-haired person with cane
Originally a pictograph showing a person with long, flowing hair leaning on a cane, representing an elder. The meaning extended from 'long hair' to 'long' in general, and also to 'elder' or 'to grow' (read zhǎng). The modern form 长 is a simplification of the traditional 長.
久 — person 人 with a stroke marking the back
Originally a pictograph showing a person from behind with a mark indicating moxibustion treatment applied to the back, the original sense of 'cauterize' (now written 灸). It was borrowed phonetically to mean 'long time' or 'enduring,' which became its standard meaning.