HolySong,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
tbody td:hover:after {
content: attr(data-th);
color: #FF0000;
}
</style>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
<script>
$(function() {
let table = $('table');
let txt = $.map($('thead td', table), ({
textContent
}) => textContent);
let len = txt.length;
$('tbody td', table).each((i, td) => td.dataset.th = txt[i % len])
});
</script>
</head>
<body>
<table>
<thead>
<tr>
<td>Заголовок 1</td>
<td>Заголовок 2</td>
<td>Заголовок 3</td>
</tr>
</thead>
<tbody>
<tr>
<td>Ячейка 4</td>
<td>Ячейка 5</td>
<td>Ячейка 6</td>
</tr>
<tr>
<td>Ячейка 7</td>
<td>Ячейка 8</td>
<td>Ячейка 9</td>
</tr>
</tbody>
</table>
</body>
</html>