Wanna know what the primary meaning of shard (preferred spelling) or sherd (secondary spelling) is, according to the Oxford English Dictionary?
Hint: It has nothing to to do with broken pottery.
I. A cleft, gap.
1. A gap in an enclosure, esp. in a hedge or bank. Now chiefly dial.
The OED gives examples from literature going back to 1000 A.D.
Wanna know what the second meaning of shard is, according to the OED?
Hint 2: Still has nothing to do with broken pottery.
†2. Used by Spenser for: ? A dividing water.
[Yr.] 1590 Spenser Faerie Queene ii. vi. sig. R7, Vpon that shore he spyed Atin stand, Thereby his maister left, when late he far'd In Phædrias flitt barck ouer that perlous shard.
Wanna know what the third meaning of shard is, according to the OED?
Hint 3: Still has nothing to do with pottery.
3. A gap or notch in the blade of a tool. dial.
Finally, we come to the fourth meaning of shard, according to the OED:
a. A fragment of broken earthenware. spec. in Archaeol., a piece of broken pottery. Phrase: to break, etc. into sherds : to reduce to fragments, break beyond repair. Cf. potsherd n. and adj. and Old English crocsceard. Sherd is now established as the normal Archaeol. spelling.
So ... according to all of this, wouldn't the actual meaning of shard seem to be the gap or the hole left in the pot when it breaks apart?
How did we come to assign to a fragment, the absence of which causes a shard, the term for the absence?
Isn't that a bit like calling a doorway the door?