diff --git a/lib/matplotlib/cbook.py b/lib/matplotlib/cbook.py
index 055d3e2f7673..8e31699142e1 100644
--- a/lib/matplotlib/cbook.py
+++ b/lib/matplotlib/cbook.py
@@ -1941,8 +1941,8 @@ def _bootstrap_median(data, N=5000):
         M = len(data)
         percentiles = [2.5, 97.5]
 
-        ii = np.random.randint(M, size=(N, M))
-        bsData = x[ii]
+        bs_index = np.random.randint(M, size=(N, M))
+        bsData = data[bs_index]
         estimate = np.median(bsData, axis=1, overwrite_input=True)
 
         CI = np.percentile(estimate, percentiles)