How has the colloquial expression 'to wing it' come about? Has it come from shooting? Or from flying ? Or some other source ?

It's been around too long for flying. According to the online etymology,
wing is used in the theatrical sense which goes back to 1790. The phrase wing it (1885) is from theatrical slang, in the sense of an actor learning his lines in the wings before going onstage, or else not learning them at all and being fed by a prompter in the wings.

Thanks.
BTW: Isn't the link delicate on the subject of willies, woollies and woollen garments ('to get the willies' )? . And there's me thinking it a reference to the Wilis of mythology