Tradition has it that חַג הַשָּׁבֻעוֹת– the Shavuot festival – marks the anniversary of the giving of the Torah at Mount Sinai.
And the Torah – הַתּוֹרָה– was given on tablets – not the kind you swallow (that’s a כַּדּוּר), but the kind made of stone.
The word the תורה uses for tablets is לֻחוֹת, with one tablet being a לוּחַ – a masculine noun, despite its looking feminine in the plural form.
Modern Hebrew takes the word לוח and uses it to mean board, such the one teachers write on.
So we’ve got:
פַּעַם, הַמּוֹרָה הָיְתָה כּוֹתֶבֶת עַל הַלּוּחַ עִם גִּיר.
It used to be (literally, once), the (female) teacher would write on the board with chalk.
Here are modern varieties of the educational לוח:
erasable board (a whiteboard)
לוח has many other meanings, including control panel, calendar and wooden plank.
I said that לוח‘s meaning in Biblical Hebrew is tablet. The kind of tablet pictured to the left, however is called, in Hebrew, a טַבְּלֶט.