The name comes from ancient Greek, it means "seed recepticle" or "seed vessel" because of the way their seeds develop in the a layer of surround tissue. It's a way to explain function during classification.
Gymnosperms mean "naked seeds", like how the word Gymnasium really means "place to be naked" XD
The thallophytes (Thallophyta or Thallobionta) are a polyphyletic group of non-mobile organisms traditionally described as "thalloid plants", "relatively simple plants" or "lower plants". They were a defunct division of Kingdom Plantae that included fungus, lichensand algae and occasionally bryophytes, bacteria and the Myxomycota. They have a hidden reproductive system and hence they are also called Cryptogamae (together with ferns), as opposed to Phanerogamae. The thallophytes are defined as having undifferentiated bodies (thalli), as opposed to cormophytes (Cormophyta) with roots and stems.