慄き	6666	15.2%
戦き	4539	10.4% <- JEs and kokugos
おののき	32621	74.4%
Unidic points 慄き to 戦く.

The refs all say 戦き but the masses, when using kanji, lean to 慄き.

@@ -14,0 +15 @@
+<misc>&uk;</misc>

戦く	2473	13.5%
慄く	4644	25.3%
戦き	4539	24.8%
慄き	6666	36.4%

plentiful yourei examples of both. Definitely fear; "恐れ慄きました。"　　Many examples carry furigana. Definitely おののき (over わななき). 

Of the 4, sankoku gives only 戦く.

daijs has 慄く and 戦く, but lists 戦く first. Don't know if we take a prescriptive position here, but "慄" actually means "fear", and wins in practice almost 2-to-1.

on twitter, maybe even 3-to-1 google:
site:twitter.com "恐れ戦き"
vs.
site:twitter.com "恐れ慄き"

Another ngram...
戦かせる	60	0.3%
慄かせる	170	0.9%

@@ -3,0 +4,3 @@
+<k_ele>
+<keb>慄き</keb>
+</k_ele>

Entry created