素っ気無い
そっけない · sokkenai · JLPT N1 · noun
cold
❄️ 素 (plain) + 気 (feeling) + 無い (none) = no feeling in it, so cold and curt
Break it into parts: 素 means plain or bare, 気 means feeling or spirit, and 無い means not there. A plain reply with no feeling in it comes across as cold, short, and blunt.
素 — silk 糸 + sheng 𠂹 (hanging threads)
Originally depicted raw, undyed silk hanging to dry, with the silk radical 糸 below and strands above. From this came the meaning 'plain, unadorned, white,' then extended to 'basic element' or 'plain/simple' in general. The 'vegetarian' sense developed later from the idea of plain, unembellished food.