ご無沙汰

ごぶさた not writing or contacting for a while; neglecting (failing) to write (call, visit, etc.)

Why it means this

無 (no) + 沙汰 (news, word — originally 'sifting', then 'a decision, a communication') — 'no word'; not having been in touch for a long time (ご無沙汰しております).

Breakdown

無ム nothingness, none, ain't
沙すな sand
汰タ washing, sieving, filtering

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