From lino (“flax”) + -aça.
linaça f (usually uncountable)
- linseed, flaxseed
c. 1250, Alfonso X, Lapidario, f. 32r:[…] ⁊ aun en otra coſa. que ſi la molieren con olio de linaça faz mas fina color q́ el uerdet ⁊ mas clara.- […] and yet another thing; that if it is ground with linseed oil it makes it finer and lighter in color than verdigris.