I'm the person you replied to in that thread, and in support of your point: after that discussion, I spent some time crawling through the proceedings of Very Large Databases (VLDB) and the ACM Digital Library, and I could find no instances of "shard" used to mean the partitioning of a database prior to 2001. (That paper is "Minerva: An automated resource provisioning tool for large-scale storage systems" in Transactions on Computer Systems, free-to-read at https://dl.acm.org/doi/abs/10.1145/502912.502915.)
Other the other hand, I found many papers citing the SHARD paper - more than the official count. That's a difficulty with citation counts of old papers: a lot of the papers citing it are also old papers, and we're not consistent at tracking the citations of old papers. Personally, I don't have a conclusion. The SHARD paper is decently cited, and its usage is close to the modern one. On the other hand, I can't find any smoking gun pre-1997 usage of "shard" in the modern meaning.
Other the other hand, I found many papers citing the SHARD paper - more than the official count. That's a difficulty with citation counts of old papers: a lot of the papers citing it are also old papers, and we're not consistent at tracking the citations of old papers. Personally, I don't have a conclusion. The SHARD paper is decently cited, and its usage is close to the modern one. On the other hand, I can't find any smoking gun pre-1997 usage of "shard" in the modern meaning.