Quincy Shibboleth
A shibboleth is a word or phrase employed to distinguish one group of people from another. Clearly if you hear somebody say ‘Quinsy’ and not ‘Quinzy’ you will immediately perceive that they are not from these parts.

The seal of the City of Quincy

New England is rich in odd pronunciation of town names, mostly because they retain the old British pronunciation, unlike their counterpart cities in the rest of America -
Worcester, Gloucester, Norfolk, Suffolk, Stoughton, Leominster, Billerica… and many more, including dear old Hough’s Neck, which many people can’t figure out. Apparently it was originally pronounced ‘Huff’s’(today - howe’s). The common Northern English family names are still Hough, Clough, and Brough - ‘huff, cluff, bruff’. Non-New Englanders might have their own distinct pronunciation of ”Hough’s Neck is part of Quincy in Suffolk County, near Boston".

Strangely enough, most visitors know how to pronounce the name of this town – you don’t find them saying ‘pl-eye-mowth’

But there are place names elsewhere in the US that can deceive New Englanders: Pierre SD is ‘peer’, Appalachia is ‘appa-LAT-cha’ to locals, Chili (near Rochester NY) is ‘tch eye leye’, Houston St in NYC is ‘how-stn’, Houston TX is ‘hyu-stn’.

British family names can be even more arcane to the uninitiated: Wymondham (wind’m), St.John (sin-j’n), St.Clair (sinclair), Dalziel (dee-yel), Fiennes (fines), McKay (m’kye), Davies (davis), Cholmondeley (chum-lee).

And there are myriad opportunities for international language difficulties:

The Scottish ‘ch’ and Welsh ‘ll’ are hard for some nationalities to pronounce.
The Khoisan languages of South Africa have voiced click sounds.
The two English ‘th’ sounds: as in ‘then’ and ‘bath’.
The rolled ‘r’ in Scottish and French.
The ‘u’ sound in French and German.
The Iberian Spanish differs from Hispanic, as in ‘Valladolid’ (bye-add-o-leeth).
… and many other distinct language sounds can betray a traveler.

Japanese speakers find difficulty in pronouncing the ‘r’ sound, approximating it with an ‘l’ sound, so that ‘refract’ and ‘reflect’ would sound the same.

Shibboleth originally comes from the Hebrew word that means "torrent of water" or "ear of grain". As Masons know from degree work, pronunciation of this word was used by the Gileadites to distinguish the Ephraimites, whose dialect lacked the "sh" sound. During this extended conflict (1370-1070 BCE), Gilead defeated Ephraim, and in order to catch and kill disguised refugees, the Gileadites put each traveler to a simple test:

And the Gileadites seized the passages of the Jordan before the Ephraimites; and it was so, that when those Ephraimites who had escaped said, "Let me go over," that the men of Gilead said unto him, "Art thou an Ephraimite?" If he said, "Nay," then said they unto him, "Say now 'Shibboleth.'" And he said "Sibboleth," for he could not frame to pronounce it right. Then they took him and slew him at the passages of the Jordan; and there fell at that time of the Ephraimites forty and two thousand.
Judges 12:5-6

Similarly the Canadian authorities identified American refugees from the draft in the 1960s by their pronunciation of the letter Z ( ‘zed’ in Canada). Fortunately the consequences of being found out were less dire!