[I'm just expanding on Wojowu's comment] A) the name solenoid for a helical coil is due to Ampère, I quote from <A HREF="https://en.wikipedia.org/wiki/Solenoid">Wikipedia:</A> > l'assemblage de tous les circuits qui l'entourent, > assemblage auquel j'ai donné le nom de solénoïde électro-dynamique, du > mot grec σωληνοειδὴς, dont la signification exprime précisement ce qui > a la forme d'un canal, c'est-à-dire la surface de cette forme sur > laquelle se trouvent tous les circuits. <sub>the assembly of all the circuits around it, to which I have given the name of electro-dynamic solenoid, from the Greek word σωληνοειδὴς, the meaning of which expresses precisely what has the shape of a channel, that is to say the surface of this form on which all the circuits are located.</sub> B) the magnetic field lines created by a solenoid are divergence free, which motivates the general name "solenoidal" for divergence free field; it might be possible to find the first incidence of this use, but the link to Ampère's solenoid seems beyond debate. <IMG SRC="https://upload.wikimedia.org/wikipedia/commons/f/f5/Finite_Length_Solenoid_field_radius_1_length_1.jpg" WIDTH="300"/>