Road map or roadmap. One word or two?

In an up-to-date corpus of 20 varieties of English, roadmap is about twice as common as road map. In a corpus built in 2104, the two forms were even-stevens, just about, but by the time of a 2018 corpus the ratio was 3:1 in favour of roadmap. It’s a historical process that has happened repeatedly. When Jane Austen wrote any body she did not mean 'any old cadaver'; body in her sense meant 'person'.

champ vs. chomp (at the bit). A short history.

In summary: champ is older as a verb in its own right, by anything between 51 and 183 years (depending on which source you go by); ‘the dictionaries’ agree that chomp is a by-form of champ; three major English dictionaries define chomp by reference back to champ; chomp in conjunction with bit is actually recorded earlier (1645) than champ at the bit, and the subsequent OED citation for chomp also includes the word bit; and Merriam-Webster shows an intransitive chomp meaning – ‘to be eager (to do)’ – that neither Collins nor the OED does.