What does 「に」 mean at the end of the 「侘しさに」?

Question

The full sentence is 「寄る辺ない侘しさに」. I did some research and found out that「に」is used with na-adjectives to basically turn them into adverbs, but「侘しい」is an i-adjective, so it doesn't make much sense.

Answer 1

First of all, is this really a full sentence? I googled and found this song. If your phrase is from this, 寄る辺ない侘しさに is a part of a sentence, not a full sentence. Please always provide the entire context.

This に is a cause/reason marker that is used with a word related to emotion or psychological reactions.

• に in コントロールに苦しまなくなった
• When do you use に to indicate a cause or reason for something?
• Grammar of nounの多さに
• Meaning of に in この狭さに

侘しい is an i-adjective, but note that it has already been nominalized with さ ("-ness") here. 侘しさ is a noun meaning "loneliness" or "melancholy".

寄る辺ない侘しさに頬杖ついてるようじゃ変わらない

(literally) If it's like you rest your cheek in your hand because of desolation with nowhere to turn, things won't change.
→ When you feel desolate with nowhere to turn, just resting your cheek in your hand won't change anything.

Even if your 寄る辺ない侘しさに is not from this song, に is still a cause/reason marker. If this is a book title, the implicit focus is how someone psychologically reacts to the 侘しさ, so it might be translated like "Loneliness Makes Me..." or "In Desolate Solitude...".

Answer 2

As noted in the comments, に is operating on a noun, in this case it means Because of / From. The sentence is incomplete.