In the well-known idiom to bark up the wrong tree, what is the underlying metaphor? In particular what is the meaning of the verb bark here?
Being a native speaker, I fully understand the normal meanings of the verb bark relating to making a loud animal-like noise. However, this does not intuitively seem to be the meaning of the word in this idiom to me. Obviously, there is also the issue of the fact that bark also appears on trees, so I wonder if to bark up a tree is to shimmy up a tree by gripping onto its bark. I have no idea. I haven't been able to find any definitions of the verb bark that don't relate to making a noise.
Is to bark up something really just to make dog noises upwards towards it?
Any answers with references/sources greatly appreciated.
Here are the definitions of bark from Oxford Dictionaries Online
[no object] (of a dog, fox, or seal) give a bark:
‘a dog barked at her’
1.1 (of a person) make a sound resembling a bark:
‘she barked with laughter’
2 [with object] Utter (a command or question) abruptly or aggressively:
‘ he began barking out his orders’
[with direct speech] ‘Nobody is allowed up here,’ he barked.
2.1 US [no object] Call out in order to sell or advertise something:
‘doormen bark at passers-by, promising hot girls and cold beer’