Young herring fish, especially those used for food, sometimes spelled 'sprats' or small fish prepared for eating.
Possibly from Dutch or Low German origins related to small fish terminology. The suffix '-ling' in English often denotes something small or young, so 'bislings' would be 'small bis' or a diminutive form of a fish name.
The '-ling' suffix is found in tons of English words for baby animals and small things—ducklings, seedlings, saplings—showing how English speakers instinctively add this sound when something cute and small needs naming!
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