Collateral adjective is an adjective que tem a different origin que a word que it refers to.
LUNAR
Lunar is an adjective relacionado a ‘moon‘.
E.g.: The lunar eclipse was beautiful!
PATERNAL
Paternal is an adjective relacionado a ‘father‘.
E.g.: Mesmo sendo um uncle, he is very paternal.
BRUMOUS
Brumous is an adjective relacionado a ‘fog‘.
E.g.: Today the weather is brumous.

IMAGE COURTESY:
• 1: https://cms.qz.com/wp-content/uploads/2018/07/lunar-eclipse-longest-21st-century.jpg?quality=80&strip=all&w=1600
• 2: http://www.drchristinahibbert.com/wp-content/uploads/2012/12/canstockphoto9326280.jpg
• 3: https://images.unsplash.com/photo-1485236715568-ddc5ee6ca227?ixlib=rb-0.3.5&ixid=eyJhcHBfaWQiOjEyMDd9&s=0b96a962d04d17d4a2d93e60a76c5b70&w=1000&q=80
IMAGE COURTESY: IMAGENS INTERNAS AO POST:
• 1: https://peopledotcom.files.wordpress.com/2018/01/super-blood-moon.jpg
• 2: https://blog.parachutehome.com/wp-content/uploads/2017/05/Fatherly_1_Retouched-1.jpg
• 3: http://www.cosmicdiary.org/fmarchis/files/2010/02/berkeley_feb18.jpg