1902, Marie Corelli, “Temporal Power”: A Study in Supremacy, London: Methuen, Chapter 18, p. 256,
The under-scent of hidden violets among moss flowed potently upon the quiet air, mingled with strong pine-odours and the salt breath of the gently heaving sea,
Source: wiktionary
[…] below her perfume lingered another perfume, more elusive, more aggressive, a man’s scent. Still staring into her eyes, he deliberately blanked his mind three times; and each time the first picture triggered in his mind by that underscent was the face of Billy Merganser.
Source: wiktionary
[…] night is when the ground heaves up the distracting odours of burrowed life: catfish and reptiles, and the musk of regeneration in scorched roots. [footnote:] Known as underscents, these odours hover beneath the buoyant smells of dung, leaves, living animals and even slaughter.
Source: wiktionary
hermetically enclosed rooms that had the persistent, unpleasant underscent of chemicals
Source: wiktionary