Definition from Wiktionary, the free dictionary
didapper (plural didappers)
- A small diving water bird frequenting rivers and fresh waters, specifically a little grebe.
- (pejoratively) One who disappears for a time and suddenly reappears.
- The writer was not heard from for some time, but when he published a new novel was known as a didapper.
- Notes on the birds of Herefordshire, Woolhope Naturalists' Field Club