次々
つぎつぎ · tsugitsugi · JLPT N3 · adverb
one by one
次々 = next + next again: 々 repeats 次, so next, next, one after another
次 (tsugi) means next, and 々 is the mark that repeats the kanji before it. So tsugi-tsugi literally says next-next, and saying next twice means things come one after another.
次 — 冫 ice + 欠 yawn/lack
Originally depicted a person (欠) sighing or hesitating, with 二 (later written 冫) marking repetition or a secondary position. The core sense developed from 'second in order' or 'next' into related meanings like 'sequence,' 'time/occurrence,' and 'inferior quality.'