grandyoudaoicibaDictYouDict[grand 词源字典]
grand: [16] The original Latin word for ‘big’ was magnus (as in magnify, magnitude, etc). However, it also had grandis. This not only denoted great physical size; it also had connotations of moral greatness or sublimity, and in addition often carried the specialized meaning ‘full-grown’. This last, together with a possibly etymologically connected Greek brénthos ‘pride’ and Old Church Slavonic gradi ‘breast’ suggest that its underlying meaning may be ‘swelling’.

French (grand) and Italian and Spanish (grande) have taken it over as their main adjective for ‘big’, but in English it remains a more specialized word, for things or people that are ‘great’ or ‘imposing’. Its use for denoting family relationships separated by two generations, as in grandmother, was adopted from Old French, and goes back, in the case of grandame and grandsire, to the 13th century, well before the independent adjective grand itself was borrowed.

But the underlying notion is as old as the Greeks and Romans, who used mégas and magnus in the same way.
[grand etymology, grand origin, 英语词源]
sunburn (v.)youdaoicibaDictYouDict
1520s, from sun (n.) + burn (v.). Sunburnt (c. 1400) is older than sunburned (c. 1500, sunne y-brent). As a noun from 1650s.