Meaning approximatly "fear(s) nothing", the word first came into use as a name for a class of large (sail) ships, dominant during the early 20:th century. The word has often appeared (occationally with slight difference in spelling, e.g. Dreadnaught).
Examples of modernised usage include (different, fictional) classes of ships, especially spacecraft within various sci-fi franchises, Spacemarine
Dreadnoughts from GW:s
Warhammer 40K franchise (sarcophagus-like warmachines which hold the remains of fallen, near-incapacitated heroes of
the Imperium) and a guitar body. The word also commonly appears as a synonym for just about anything "big" or, in some cases, strong, impressive of awe-inspiring.