Keep your head/chin/pecker up

Question

We have two situations that the following sentences can be used in:

1. Keep your head up.
   
2. Keep your chin up.
   
3. Keep your pecker up.
   

a. When you want someone to be hopeful again after a setback.
b. When for instance a soccer player keeps head down when he is playing and his / her coach wants to ask him / her to keep head up when he is playing, (or in similar situations.)

To me, these three sentences mean the same thing and the only point that should be considered is that the last one sounds too informal (maybe impolite)

I wonder which sentence is used for which one of the two cases that I wrote above. (I think all three sentences have both of the usages.)

Answer 1

Of the three examples you give, "keep your chin up" is the only one which really means to be positive.

"Keep your head up" makes sense as an instruction, but is not particularly an idiom. A hairdresser might ask you to keep your head up so he can cut your hair properly. "Keep your chin up" is a popular idiom, and the inference is that your head is bowed slightly due to a low mood.

"Keep your pecker up" did once mean the same thing - a "pecker" was slang for nose and mouth area, like a bird pecks with its beak; but a pecker can also be a slang word for a penis, so even though the idiom may retain its meaning it is often used as a double-entendre.

Another similar expression is "keep your spirits up".