Common or garden was originally used to describe a plant in its most familiar domesticated form, e.g. the common or garden nightshade.
1964 - Leonard Woolf Letter - I certainly do not agree that the unconscious mind reveals deeper truths about someone else than plain common or garden common sense does.
Related Idioms :
wear no underpants - informal
the common touch
the ability to get on with or appeal to ordinary people
An obsolete sense of common (which comes from Latin communis meaning affable) may have influenced this phrase, as may a Shakespearean phrase used in his play about the great exponent of the common touch, King Henry V, on the eve of the battle of Agincourt : a little touch of Harry in the night.
1910 - Rudyard Kipling - If you can talk with crowds and keep your virtue, Or walk with
Kings - nor lose the common touch.