I dislike abbreviations for this exact reason. Both your and the above responses are different. Clearly it's not well known abbreviation.

Personally Identifying Information. It's pretty common to anyone who works with PII. Also the top Google search result for PII.

sorry, i probably shouldn't have replied. difficult to know whether the context is "quickly help me understand what this means" or "give me a precise answer", but for the web, with a technical audience, i should lean more towards the latter...