free from agitation or disturbance; tranquil, calm, serene, placid, quiet, still, peaceful ...1638 obs. rare
from Latin tranquillus (tranquil adj.) + -ous
FIRST DOCUMENTED USE
1638 - see EXAMPLE below
"...Then out of doores with Tarquin, what's he that may fit in a calme valley, and will chuse to repose in a tempestuous mountaine, but a mad-man? that may live in tranquillous pleasures, and will seek out a kingdomes cares, but a mad-man? who would seek innovation in a Common-wealth in publike..."
From: The Dramatic Works of Thomas Heywood (1874)
The Rape of Lucrece
- Thomas Heywood