AphDem3.44:13 :ܘܐܝܬ ܕܨܐ݁ܡ ܕܢܥܒܕ ܣܝܓܐ ܠܦܘܡܗ݂ ܕܠܐ ܢܡܠܠ ܡ̈ܠܐ ܣܢܝ̈ܬܐ‏ : there is one who fasts so as to put a fence on his mouth so that he might not speak hateful words
See the entire entry for syāḡ, syāḡā v.n. fencing in, fence