Definition & Meaning of "by gum"in English

What is the origin of the idiom "by gum" and when to use it?

By gum is an exclamation used to emphasize a statement, express determination, or mild astonishment. It appeared in English in the 18th century as a euphemistic substitute for "by God," allowing speakers to convey strong feeling without swearing. People used it in everyday speech, literature, and storytelling to stress a point, show resolve, or react to surprising events. Today it is inoffensive, slightly old-fashioned, and folksy, often adding emphasis or a colorful tone to statements without being vulgar.