TITLE: Who started the "-oid" suffix fashion in math?
QUESTION [16 upvotes]: There are lots of structures which have name suffixed by "oid".  Off the top of my head, matroid, greedoid, perfectoid, causaloid...
Who started this? AFAIK, "matroid", by Whitney, was a start, and led the way to several combinatorial oids.  However, the Cardioid has had its name for some centuries now, so the use of the suffix is old.
Still, it seems a bit different to name a family of specific objects, and to name some sort of abstract structure.

REPLY [4 votes]: Though this might not be what you are expecting, I will explain you "oidification" or horizontal categorification as I understood (Experts are fell free to add or edit as necessary). This is the process that generalizes a "certain type of category with a single object" to "such type of categories with multiple objects". This is done mostly via "enriching" the initial category $\mathcal{C}$ over another monoidal category $\mathcal{K},$ which roughly says homsets (set of arrows two objects) of $\mathcal{C}$ are replaced by objects of $\mathcal{K}.$
Examples include




X
X-oid
Enrichment




monoid
Category
categories enriched over Set


Category
2-Category
categories enriched over Cat


Group
Groupoid



Ring
Ringoid
category enriched in tensor category Ab


Quantale
Quantaloid
category enriched in suplattices


Algebr
Algebroid
category enriched in Vect or RMod


C*-algebra
C*-category
*-category enriched in Ban




You can find more details ringoid, and algebroid here. But as far as I know Hopf algebroids and Lie algebroids does not fit into this general definition of algebroids, but still multi-object generalizations of their counterparts.
Also, it should worth remind that not every enrichment of a categories consider as an "odification". For example (Lawvere) generalized metric spaces is a  category enriched in the monoidal poset category $([0,\infty],\ge),$ where the monoidal product is taken to be addition.