いっそ
いっそ · isso · JLPT N1 · adverb
might as well
いっそ comes from 一層 (ittō, one more level): go one step further, so it means rather or might as well
一層 (ittō) means one more level or degree. That sense of going a notch further gave いっそ its meaning of rather, sooner, or might as well when choosing between options.