An inode is a record in a disk table, which contains information about a file or folder such as its size, owner, device node, socket, pipe, etc., except data content and file name. The number of inodes on your account equals the number of files and folders you have on it.
To reduce the number of inodes your account uses:
1. Remove all files/folders you don’t need
There may be some backup files/folders placed outside your public_html web root folder or situated inside it, which are generated by an extension installed inside your website application, i.e. Akeeba backup for Joomla. If you need some of these files you can download them locally on your computer through FTP and after that remove them from your hosting account.
2. Check the number of cache files you have
Applications such as Joomla can generate a lot of cache files, which are increasing the amount of the inodes for your hosting account. You should regularly check your cache folder and reduce the number of cached files you keep. Most of the applications, which are caching content have the so-called Purge cache functionality inside their administrative area, which can be used for clearing such files.