the.com/shingle

means A thin, flat piece of wood, slate, or other material laid in overlapping rows to waterproof a roof or wall — or, in its other life, a small sign hung outside a professional's office.

from Likely traces back to Latin 'scindula' (a split piece of wood), via a Germanic path into Old English — the word for the object matches the method: shingles were literally scindere, 'split' or 'cleaved,' from logs before being laid in overlapping rows. The 'hang out your shingle' sense (meaning to open a small professional practice) is a later American coinage, borrowing the word for the humble wooden sign shaped and sized like a roofing shingle that tradespeople and doctors would nail up to announce themselves.