Field collection item table names in mysql
In Drupal 8 the field tables are created as [ENTITY_TYPE]__[FIELD_NAME] and [ENTITY_TYPE]_revision__[FIELD_NAME] in database. The [ENTITY_TYPE]__[FIELD_NAME] is a main field table where latest revision data of entity field is stored. Where as [ENTITY_TYPE]_revision__[FIELD_NAME] is field revision table where all revision data is stored for a field.

In your case I think your Drupal/Database has some issue, because of which the table name has random character (10 characters) hexadecimal in it. I'm not sure of exact reason of this, but I too have notice this sometime in my Drupal Site (only twice one in D7 and one in D8) not every time.

In such case, where you're unsure of which table is used for which field, you can use name and value column in key_value table to get field table mapping. The name column contains, the entity and field name and value column contains serialized array of field schema stored in blob type. The name column format is as below:

[ENTITY_TYPE].field_schema_data.[FIELD_NAME]

So if I've field named as field_test in field_collection_item entity, then the mapping will be stored as field_collection_item.field_schema_data.field_test in key_value table. Check the screenshot below:

Screenshot 1: key_value table showing record of field_test field.


Screenshot 2: value column data from key_value table for field_test field.


I know this is not a better solution but, if table name doesn't has field name in it you can use data in value column in key_value table, you can find which table is used for which field.

Hope this helps.