I can't reproduce this on my Mac laptop (using Python builds from MacPorts). Numbers for both x**2 and x*x are fairly stable across Python 3.2 to Python 3.10. There's some variation, but nothing close to the same extent that Steven is seeing.

Here are my raw numbers:

lovelace:cpython mdickinson$ /opt/local/bin/python3.2 -m timeit -s "x=115" "x*x"
10000000 loops, best of 3: 0.031 usec per loop
lovelace:cpython mdickinson$ /opt/local/bin/python3.3 -m timeit -s "x=115" "x*x"
10000000 loops, best of 3: 0.0297 usec per loop
lovelace:cpython mdickinson$ /opt/local/bin/python3.4 -m timeit -s "x=115" "x*x"
10000000 loops, best of 3: 0.0286 usec per loop
lovelace:cpython mdickinson$ /opt/local/bin/python3.5 -m timeit -s "x=115" "x*x"
10000000 loops, best of 3: 0.03 usec per loop
lovelace:cpython mdickinson$ /opt/local/bin/python3.6 -m timeit -s "x=115" "x*x"
10000000 loops, best of 3: 0.0312 usec per loop
lovelace:cpython mdickinson$ /opt/local/bin/python3.7 -m timeit -s "x=115" "x*x"
10000000 loops, best of 5: 28.7 nsec per loop
lovelace:cpython mdickinson$ /opt/local/bin/python3.8 -m timeit -s "x=115" "x*x"
10000000 loops, best of 5: 32 nsec per loop
lovelace:cpython mdickinson$ /opt/local/bin/python3.9 -m timeit -s "x=115" "x*x"
10000000 loops, best of 5: 33.5 nsec per loop
lovelace:cpython mdickinson$ /opt/local/bin/python3.10 -m timeit -s "x=115" "x*x"
10000000 loops, best of 5: 32.3 nsec per loop
lovelace:cpython mdickinson$ /opt/local/bin/python3.2 -m timeit -s "x=115" "x**2"
1000000 loops, best of 3: 0.249 usec per loop
lovelace:cpython mdickinson$ /opt/local/bin/python3.3 -m timeit -s "x=115" "x**2"
1000000 loops, best of 3: 0.224 usec per loop
lovelace:cpython mdickinson$ /opt/local/bin/python3.4 -m timeit -s "x=115" "x**2"
1000000 loops, best of 3: 0.221 usec per loop
lovelace:cpython mdickinson$ /opt/local/bin/python3.5 -m timeit -s "x=115" "x**2"
1000000 loops, best of 3: 0.213 usec per loop
lovelace:cpython mdickinson$ /opt/local/bin/python3.6 -m timeit -s "x=115" "x**2"
1000000 loops, best of 3: 0.235 usec per loop
lovelace:cpython mdickinson$ /opt/local/bin/python3.7 -m timeit -s "x=115" "x**2"
1000000 loops, best of 5: 204 nsec per loop
lovelace:cpython mdickinson$ /opt/local/bin/python3.8 -m timeit -s "x=115" "x**2"
1000000 loops, best of 5: 217 nsec per loop
lovelace:cpython mdickinson$ /opt/local/bin/python3.9 -m timeit -s "x=115" "x**2"
1000000 loops, best of 5: 245 nsec per loop
lovelace:cpython mdickinson$ /opt/local/bin/python3.10 -m timeit -s "x=115" "x**2"
1000000 loops, best of 5: 230 nsec per loop