IshDan 113(16) :ܥܬܝܩ ܝܘ̈ܡܬܐ ܥܠ ܩܕܝܡܘܬܗ ܘܡܬܘܡܝܘܬܗ ܘܒܪܘܝܘܬܐ ܡܘܕܥ‏ : "the ancient of days" indicates his antiquity, his eternality, and creative power
See the entire entry for mṯōmāyū, mṯōmāyūṯā n.f. eternality