Re the definition of 'Lark' [in 'lark about']. While the offers here are certainly believable (and as a Yorkshireman I can see how the pronunciation could be misunderstood), I've always assumed that lark (or indeed lake, in the Yorkshire sense) came from the scandinavian (perhaps Norwegian or Old Norse?) 'Lek' as in 'Fartlek' (no sniggering, please) meaning literally speed-play - hence lek 'to play'?