On a MariaDB server on Windows with lower_case_table_names=2 (i.e. names are stored as declared, but compared in lowercase), table names get converted to lowercase when dropping an index. The following two SQL statements reproduce the issue:
CREATE TABLE `TestTable` (`TestColumn` INT NULL, INDEX `TestIndex` (`TestColumn`)) ENGINE=MyISAM;
DROP INDEX `TestIndex` ON `TestTable`;
After the first line is executed, a table called "TestTable" exists.
After the second line is executed, the table is renamed to "testtable".