Explanation

In an Excel worksheet, the first cell is labeled as A1 due to the following reasons:

1. Grid System: Excel uses a grid to organize cells, with rows and columns.
2. Rows Labeled by Numbers: Rows are labeled using numbers (1, 2, 3, etc.).
3. Columns Labeled by Letters: Columns are labeled using letters (A, B, C, etc.).
4. First Cell Location: The first cell is located at the intersection of row 1 and column A, hence labeled A1.