https://getoutside.ordnancesurvey.co.uk/guides/the-history-of-pub-names/
\\Black Boy
Now a rather controversial pub name, records of ‘Black Boy’ inns go back at least 250 years. There are four potential origins of the name – and no-one’s really sure which is the real explanation! The pub could be named after:
a character with skin darkened by their work, like chimney sweeps or miners covered in soot or coal-dust.
King Charles II, who was nicknamed ‘Black Boy’ by his mother, Henrietta Maria of France because of his dark hair and complexion. The name was adopted by Charles’ supporters fighting for the restoration of the Monarchy in the 1650s. Inns using the Black Boy name were possibly declaring their royalist allegiance against Oliver Cromwell’s parliamentarians.
The least watertight etymology is that they’re named after local dark-coloured shipping signals, the name being a misspelling of Black Buoy.//