It is quite interesting that the later 1st century CE Aramaic translation of Isaiah chapter 7 is very similar to our other sources, except for this verse! It reads completely differently, as this:
For the sake of a New Covenant, you shall be informed to prepare the way and to build a column to tie the two kings. Keep the land that you are exalted in from before the two kingdoms.
ܡܵܪܝܵܐ ܢܲܝܬܹ̇ܐ ܥܠܲܝܟ: ܘܥܲܠ ܥܲܡܵܟ݂: ܘܥܠ ܒܹܝܬ̣ ܐܲܒ̣ܘܼܟ݂: ܝܵܘ̈ܡܵܬ̣ܵܐ ܕܠܵܐ ܐܸܬ̣ܵܘ ܡ̣ܢ ܝܵܘܡܵܐ ܕܐܲܥܒܲܪ ܠܐܲܦܪܹܝܡ ܡ̣ܢ ܝܼܗܘܼܕ݂ܵܐ ܡܲܠܟܵܐ ܕܐܵܬ̣ܘܿܪ.
Why is it so different? We have no idea!