Sage oil is reputed to be good for the memory. In research conducted at universities in Newcastle and Northumbria, sage oil elevated a chemical in the brain often depleted in Alzheimer’s patients.
Sage advice is smart advice; a sage was an experienced, judicious, wise man, and wisdom requires memory of experience. Speakers of Middle English might refer to the sage Robert or the sage Jane. First citation in English from 1297, The Chronicle of Robert Gloucester, which is the 93rd-most cited source in the Oxford English Dictionary, the source for anlace, “a short two-edged knife or dagger, broad at the hilt and tapering to the point,” the verb forsloth, “to lose, miss, neglect, spoil, or waste through sloth,” and plud, “a pool or puddle.” (Robert apparently wrote only the last 3,000 lines of the chronicle, which is a vernacular history of England.)
The word also appears in Piers Plowman. From Latin sapere, “to be wise,” the present participle of which is sapiens, as in Homo sapiens. The plant name is from the Old High German salbeia. No apparent connection.