Could is used to talk about ability or possibility, especially in the past, or to make polite requests and suggestions.
It comes from Old English “cuðe,” the past tense of “cunnan” (to know, to be able), which is related to “can.” Spelling later changed to match the pattern of “would” and “should,” even though the “l” is not pronounced.
The silent “l” in could is a spelling copycat—it was added to look like would and should, not because anyone ever said it. The word began with the idea of ‘knowing how’ to do something, which quietly links knowledge and ability.
Complete word intelligence in one call. Free tier — 50 lookups/day.