Trivial/ignorable/bikeshed painting: This is more than pushing attributes. You are converting the list into a list of items into a list of dicts with the item as a key, plus other annotations.  Therefore, I want a more descriptive name.  I'm also tempted to ask that you put this in utils since it is a generic data manipulation, but <shrug> on that one.

The whole function could almost be a one-liner.

list.map(function(item) {
    return Y.merge(additions, { unit: item });
}

That kind of makes me wonder if it is worth breaking it out: we could just do the logic in the forEach loop above and remove this.

What do you think?

Even if you want to leave it where it is, I suggest simplifying it with Y.merge.