Guy: The word 'guy' (as in a man) comes from Guy Fawkes, who planned to execute the king of England. In celebration of the king escaping assasination, people burn effigies of him, usually made of rags. A man who looked scruffy/disheveled would sometimes be compared to these effigies, and be called a 'guy'. From there, the word eventually lost its negative connotation and now can refer to any man (and in the plural form - 'you guys' - to people of any gender).
-ly (the suffix on 'gently', 'slowly' etc.): This suffix comes from Proto-Germanic word *-līkaz, meaning body. It then started being used to describe things that had the body of (as in is similiar to) some other thing (something could be 'tree-like', for example), and later started to be applied to verbs (e.g. 'quick-like'). It was then shortened to 'ly'.
Robot: Robot comes from the slavic word 'robota', meaning forced labour or servitude. Its modern meaning comes from a play named 'Rossum’s Universal Robots' where manfactured beings are used as slaves to do stuff humans didn't want to do.
Malaria: 'Malaria' comes from Italian 'mal aria' (bad air) as it was once thought that malaria was caused by poisonous air coming from bogs and marshes.
Ampersand: An ampersand is the 'and' symbol (&), and was once considered part of the alphabet. People would say 'and per say and' (and by itself) to distinguish the character from the word. 'And per se and' later morphed into 'ampersand'.