solar [LME] This is from Latin solaris, from sol ‘sun’, a base shared by mid 19th-century solarium, a use of a Latin word meaning both ‘sundial’ and ‘place for sunning oneself’. Solar power was first discussed in the early 20th century. From the same source comes solstice [ME], the second half of which comes from Latin sistere ‘to stop’; and from Italian, based on Latin, parasol [E17th] from parasole, formed from para- ‘protecting against’ and sole ‘sun’. Old English sun is from the same Indo-European root.