As keen as mustard British old-fashioned simile
"As keen as mustard" is also known as "keen as mustard".
Very eager, enthusiastic, excited and interested in something
They are as keen as mustard to plan a 3 day trip.
Unlike other children at the same age, Sam is as keen as mustard to learn about IT.
She was as keen as mustard to begin her new job until she realised it was so boring.
If you like something very much or find something appealing or interesting to you, it strikes your fancy.
To express great excitement or absurd joy when staring at someone or something
This phrase is believed to have originated from mustard. Mustard was, and till now is a must ingredient for cooking beef because it would add flavor and increase appetite, and it was soon associated with this enthusiasm. The phrase “as keen as mustard” is also stated to have been referred by William Walker in his book Phraseologica Anglo-Latina, or Phrases of the English and Latin Tongue published in 1672. And then, it was used again by F. Smith's in his work Clod-pate's Ghost in the year 1679 which clarified the meaning of the phrase.