What's the difference between gruf and grum?

Gruf

---

Definition:

• (adv.) Forwards; with one's face to the ground.

Example Sentences:

• (1) Andy darkly gruffing and grumping and breaking off every few minutes to check the Guardian homepage on his iPhone.

Grum

---

Definition:

• (a.) Morose; severe of countenance; sour; surly; glum; grim.
• (a.) Low; deep in the throat; guttural; rumbling; as,

Example Sentences:

• (1) She has projects lined up with many of the new exponents of disco, including Goldroom , Grum and Mighty Mouse .