Lang is short for Language.
Here is an explanation for Limey -
Limey is an old American and Canadian slang nickname for the British, originally referring to British sailors.
The term is believed to derive from lime juice, referring to the Royal Navy and Merchant Navy practice of supplying lime juice to British sailors to prevent scurvy.
The benefits of citrus juice were well known at the time thanks to the acute observations of surgeon James Lind who noticed that the cabbage-eating Dutch had fewer problems with scurvy.
Limes replaced lemons due to limes being more readily available from Britain's own Caribbean colonies. Lemon juice was reintroduced after scurvy again became a problem due to lime juice lacking sufficient vitamin C.
The term is thought to have originated in the Caribbean in the 1880s. A false etymology is that it is a derivative of "Corr-blimey" ("God blind me!" or "God blight me!").
"Limey" reference to British citizens may also have origins of reference to the white cliffs of Dover composition of lime.