hobby horse

See also: hobbyhorse, and hobby-horse

English

A child with a hobby horse (sense 2).

A man with a hobby horse (sense 4).

A dandy or hobby horse (sense 5).

English Wikipedia has an article on:

hobby horse

Wikipedia

hobby horse (plural hobby horses)

(originally) The Irish hobby, an extinct breed of horse.
A child's toy consisting of a (usually wooden or cloth) horse's head mounted on a stick.
(figuratively) A topic about which someone loves to talk at great length.
Don't ask him about global warming: it's his favourite hobby horse, you'll never get away.
- 1886, Peter Christen Asbjørnsen, translated by H.L. Brækstad, Folk and Fairy Tales, page 250:
  The squire was now on his hobby-horse, as we say; he had placed the old worn fur cap by his side on the sofa, leaving his bald head and grey hairs exposed.
A puppet-like costume used in some traditional dances and festivals that gives its wearer the appearance of a man on horseback.
(cycling, historical) An early bicycle with no pedals or brakes.
Synonyms: dandy horse, draisienne
- 2015, Chris Boardman, The Biography of the Modern Bike: The Ultimate History of Bike Design, Hachette, →ISBN, page 10:
  British users rechristened the baron's invention the hobby horse then the dandy horse, because draisines became very fashionable with Regency gentlemen.