The phrase "frog in one's throat" is used to describe a temporary hoarseness or difficulty in speaking, usually due to a minor irritation or mucus in the throat. 

The exact origin of the phrase is not definitively known, but there are a few theories about how it came into common usage. The phrase likely comes from the imagery of a frog being stuck in one's throat, causing croaky, hoarse, or rough speech. This comparison effectively conveys the sensation of having something obstructive or irritating in the throat that disrupts normal speech. 

The phrase appears to have become popular in English in the late 19th to early 20th centuries. It has been used in literature and everyday language to describe the common experience of throat irritation that affects one’s voice. Some sources suggest that the phrase may have been popularized by medical advertisements in the 19th century. 

Remedies for throat irritation or hoarseness sometimes used the term "frog in the throat" to describe the symptoms their products aimed to alleviate.